Quantity is a quality all its own

So, as I look at various setups for my Dread List (from hence forth known as the Vahallan Immortals),  I have really begun to think about what I am using and why I use.  Currently, my three shooty dreads are running a TL Lascannon and a Missile launcher each.  I have heard on the interwebs that the 2x TL autocannon setup is really good as well.  Thus, I ran some numbers (hopefully they are right).  I was basically using a AV 11 vehicle destroyed as my measure for success.  I wanted to know which setup was better and I applied it to my 3 shooty dreads to see what could be accomplished in a turn.  Here is what I found:

I started with TL autocannon dreads

Autocannons shoot twice, so that would be 4 shots per Dread

With BS 4 and TL, there is an 88% chance of hitting with TL autocannon= 1.777 hits x 2 TL Autocannons=  3.554 hits

Being S7, I need a 5 or 6 to pen, so there is a 33% chance to penetrate AV11= 1.18 penetrating damaging hits

After penning, there is 33% chance to destroy AV11 with a roll of 5 or 6= .389 destroyed vehicle results per turn

With 3x TL Autocannon dreads= 1.168 destroyed AV11 vehicles per turn

So translation: 3 Dreads with 2x TL autocannons shoot 12 S7 shots and end up statistically killing a little over 1 vehicle per turn outright. 

Next I went on to look at the TL Lascannon/Missile launcher Dread.

Lascannon

Lascannons shoot only 1 shot

There is an 88% chance of hitting with TL Lascannon= .88 hits per shot

Next, there is a 66% chance to penetrate AV 11= .58

There is a 33% chance to destroy AV11= .191 destroyed vehicle results per turn

With 3x TL Lascannon dreads= .574 destroyed  AV 11 vehicles per turn

Missile Launcher

There is a 67% chance of hitting with missile launcher= .67 hits per shot

Next, there is a 50% chance to penetrate AV 11= .335 penetrating hits

There is a 33% chance to destroy AV 11= .11 destroyed vehicles results per turn

3x missile launcher dreads= .333 destroyed AV 11 vehicles per turn

Total destroyed AV 11 vehicles per turn for TL lascannon/missile launcher= .907

So, translation: I will kill just shy of 1 vehicle per turn with these dreads. 

Conclusion:

The TL autocannon dreads win, but probably because they lob a much greater volume of shots, double in fact. 

Advantage of 3x TL autocannon dreads vs. TL lascannon/missile launcher dreads= .261 destroyed results per turn

Of course, I only calculated vehicle destroyed results.  It could be that if we included glancing results and then shaken, stunned, weapon destroyed, and immobilized results on the penetration chart, that TL lascannon/Missile Launcher dreads might fair just as well. 

One thing I really do see, is the need for supporting long range and melta fire.  Luckily in my current army list, I have these things.  So, let me know what you think.  Are TL autocannon dreads actually better than lascannon/missile launcer dreads?  Is my math right?  Still hoping to try out the list next week, so will give some thoughts and possibly a short report after I am done.  Look for an updated list to follow.